adj. 25B6; adjective UNQUESTIONABLE, undoubtable, indisputable, unarguable, undebatable, incontestable, undeniable, irrefutable, incontrovertible, unmistakable, unequivocal, certain, sure, positive, definite, absolute, conclusive, watertight; beyond doubt, beyond the shadow of a doubt, beyond dispute, beyond question, not in question, not in doubt.
doubtful.